/Engine/Source/Runtime/Slate/Public/Framework/Text/CharRangeList.h
Examples: "aT." < Letters 'a' and 'T', dot and underscore. "a-zT." < All letters from 'a' to 'z', letter 'T', dot and underscore. "a-zA-Z0-9." < All lowercase and uppercase letters, all digits, dot and underscore. "a-zA-Z0-9-\." < All lowercase and uppercase letters, all digits, minus sign, backslash, dot and underscore.
bool InitializeFromString ( const [FString](API\Runtime\Core\Containers\FString) & InDefinitionString )